Process for hydrogenating aliphatic carboxylic acid anhydrides



Patented Mar. 3, i942 Wilbur A. Lazier, Wilmington, DeL, assignor to E. I. an Pontde. Nemours & Company, Wilming'ton, per, a corporation 01 Delaware No Drawing. Application January 2, 193

Serial No. 584,574

6 Claims. (Cl. 260-638) I g hydrogenating catalyst under a superatmospheric This invention relates to a process for catalyti- 'cally hydrogenating organic compounds and more particularly it pertains to the catalytic hydrogenation of carboxylic' acid anhydrides. This application is in part a continuation of my copending applications Serial No. 445,224, filed April 17, 1930, Serial No. 470,238, filed July .23, 1930, and Serial No. 520,473, filed March 5, 1931.

For many years the successful hydrogenation of carboxylic acids and derivatives thereof has been accompanied by considerable diiilculty, and

in the main, it has been practically impossible to carry out known processes with any degree of success on a commercial scale. The processes heretoiore known to the art which are at all ieasible involve an indirect procedure attended with considerable tedious detail and expense. One known process, namely that described by Bouveault and Blane in 1904, comprises reducing an ester of a carboxylic acid to the corresponding alcohol by means of metallic sodium in anhydrous alcoholic solution. Another method, according to Rosenmund, depends on the hydrogenation of an acid chloride to the aldehyde in the presence of a palladium catalyst. Sabatier and Mallhe have described a reaction in which acetic acid may be reduced to acetaldehyde by passing it together with formic acid or carbon monoxide over a mangenese oxide catalyst.

It has .been discovered, in accordance with the teachings of the present invention, that, under suitable conditions, and in thepresence of a properly selected catalyst, anhydrides of carboxylic acids can be readily and .inexpensively hydrogenated to produce corresponding'alkyl compoundsior example alcohols.

One object or the invention relatesto the process for successfully hydrogenating anhydrides of carboxylic acids. A more specific object pertains to the use of hydrogenating metal chromites preferably in the form of a mixture'of such chromites for the hydrogenation of anhydrides of carboxylic acids. Other objects of the invention will be-- come apparent from the following detailed description of the invention.

The anhydrides of carboxylic acids which may be hydrogenated in accordance with the present invention are those of the aliphatic carboxylic acids containing more than one carbon atom per carboxyl group. These include the anhydrides of acids obtained by the hydrolysis of naturally occurringfats and oils. The general method in-- volved in transforming these anhydrides tothe corresponding alcohols comprises contacting a pressure and at an elevated temperature.

The following examples are given for the purpose of illustrating specific methods for making catalysts that may be used for the carrying out of the reaction.

Example 1 A hydrogenation catalyst is prepared as follows: 23 grams of cadmium nitrate, 24 grams of copper nitrate, and 245 grams of zinc nitrate are dissolved in 500 cc. of water and mixed at ordinary temperature with an equal volume of water containing 126 grams of ammonium bichromate and 75 cc. of 28% ammonium hydroxide. After stirring, the mixture is exactly neutralized with additional ammonium hydroxide and allowed to Q settle. After several washes by decantation, the precipitate is dried, ignited .at 400 C. and compressed into tablets or grains suitable for use in catalytic gas apparatus.-

. Example 2 A copper catalyst is prepared by fusing 8 parts by weight of pure copper oxide with one part of zinc oxide and one part of magnesium oxide. The cooled mass is crushed, screened, and reduced at 150 C. in a stream of diluted hydrogen containing carbon dioxide and 20% hydrogen.

Example 3 A copper chromite catalyst is prepared by igniting copper ammonium chromate to its decom- 25 cc. of the catalyst per hour at a temperature of 325 C. and at a pressure of 2600-3200 lbs. per

square inch.

The following example is given for the purpose oi specifically illustrating the applicant's invention.

Example 4 1 A zinc chromite catalyst promoted with copper chromite was prepared by igniting a coprecipitat'ed mixture comprising 0.9 mole of zinc ammonium chromate and 0.1 mole of copper ammonium chromate. One hundred cc. of the briquetted' catalyst was placed in a high-pressure mixture 0! the anhydrides and hydrogen with a 5.5

tube and heated to 390 C. At this temperature and at a pressure of 2800 lbs. per square inch, acetic anhydride was pumped over the catalyst at the rate of 100 cc. per hour together with an excess of hydrogen flowing at the rate of about seven cu. ft. per hour. The liquid reaction products were condensed under pressure and separated from the excess gas. A careful analysis of the condensate gave the following results:

Weight percent in condensate Compound formed Acetic anhydride ummu wma flow of" the material to be tre ted over the catalyst have been indicated in the above examples, it will be apparent that these factors may be varied within wide limits. The preferred temperature range is in the neighborhood of '300-40.0 C., the

exact temperature used depending somewhat on the catalyst composition selected for a given reaction. The invention is not to be limited to the preferred lower limit of 300 C. since temperatures in excess of 200 C. areoperable. The process depends upon the use of elevated pressure, the range of pressure which may be used varying from 10 atmospheres up to the limit of a pressure which the apparatus will withstand, the preferred pressures being in the neighborhood of The rate at which the acid anhydride may be pumped over the catalyst is a function of the catalytic activity and also of the molecular weight of the compound. An active hydrogenating catalyst will ordinarily convert about 4 to 8 times its volume of acid anhydride per hour.

.Higher rates of flow may be employed at the expense of slightly lower conversions.

Catalysts especially suitable for the purposes of the present invention may consist of a mixture of diflicultly reducible oxides of hydrogenating metals. I prefer to use compositions in which the oxides are in the form of the chromites of the metals. An effective catalyst comprises the mixture of chromites or' chromates of different hydrogenating metals and containing also some of the oxides of those metals. A catalyst of this type may be prepared by the manner described in Example 1. Mixed catalyst compositions of this type have a catalytic effect in general which is greater than the sum of the effects of its constituent oxides or chromites. The mixed chromite catalyst preferably contains a small amount of chromite or oxide of one or more hydrogenating metals whose oxides are readily reducible together with a chromite of one or more hydrogenating metals whose oxides are diflicultly reducible, the proportions of the dimcultly reducible chromites and of the easily reducible oxides or chromites being capable of wide variation. Suitable hydrogenating metals whose oxides are readily reducible are silver, cadmium, copper, lead, mercury, tin, bismuth, iron, cobalt and nickel. Hydrogenating metals whose oxides are difiicultly reducible are magnesium, zinc and manganese. In the above type of catalysts these oxides are combined and/or intimately associated with chromium oxide.

300 lbs/sq. in. or above about 2000 lbs/sq. in.

The pressures desired will vary according to the specific acid derivative under treatment and upon the amount of conversion desired.

It will be apparent'from the above examples that the method of my invention is applicable to anhydrides of carboxylic acids in general, but may be used with particular advantage for the hydrogenation of the anhydrides of aliphatic monobasic acids to the corresponding monohydric alcohols. It is also valuable for the hydrogenation of anhydrides of dibasic and other polybasic acids to the corresponding glycols and,

other types of alcohols. It is especially adapted to the hydrogenation of the anhydrides of acids having more than one-carbon atom per carboxyl group. It may also be employed eilectively for the hydrogenation of anhydrides of hydroxy and ketonic acids, yielding thereby useful glycols. It

is also apparent that mixtures of anhydridesof aliphatic carboxylic acids may be converted to mixtures of alcohols. For example, I may take the anhydrides of the mixed acids contained in a fat such as coconut oil and without separation into their various components convert them to, a mixture of the corresponding alcohols of high molecular weight. The hydrogenation of anhy-' drides yields the corresponding alcoholsand a greater or lesser per cent of ester formed by interaction of'the higher monobasic alcohols and the carboxyl radical.

The ratio of hydrogen to acid anhydride may be varied over a wide range, but I prefer to use about 5 to 10 moles of hydrogen per mole of acid derivative for most conversions.

While the catalyst previously described is preferred because of the higher conversion obtained, it is to be understood that other good hydrogenating catalysts are suitable. These hydrogenating catalysts may be either in the form of reduced metals or oxides of the mixtures of the same. For example, I may use such reduced metals as copper, tin, cadmium or lead and in certain cases iron and nickel. Good results are obtained with fused reduced copper oxide alone. The copper oxide catalyst may be promoted with the well known oxidepromoters, for example, the difiiciiltly reducible hydrogenating metal oxides, as is illustrated in Example 2. Hydrogenating metal oxide catalysts are likewise suitable for the reaction. These oxide catalysts may likewise be promoted by the addition of other oxides preferably those having a more acidic character. Examples of promoting oxides are the oxides of chromium, molybdenum, tungsten and titanium. Those oxide catalysts which are promoted by the addition-of chromium oxide are highly satisfactory. Thus, zinc oxide or copper oxide to which'- has been added amounts of chromium oxide which may be varied within wide limits, are quite effective. As particularly good catalysts, I may use chromates or chromites of hydrogenating metals. 'The preparationof catalysts of this latter type containing a single hydrogenating metal are described in my U. S. Patents 1,746,782 and ing metal to its spontaneous decomposition temperature.

The above description and specific examples are to be considered-as illustrative only and not 400 C. and at a pressure above about 2000 lbs/sq.

4. The process of producing alcohols which comprises treating with hydrogen an anhydride as limiting the scope of the invention. Any 5 of an aliphatic carboxylic acid, said acid containmodification or variation therefrom which conforms with the spirit of the invention is intended to be included within the scope of the claims.

1. The process of producing alcohols which comprises treating with hydrogen an anhydride of an aliphatic carboxylic acid containing more than one carbon atom per carboxyl group at a temperature in excess of 200 C. and under a pressure in excess of 10 atmospheres, in the presence of copper oxide intimately associated with an oxide of chromium.

2. The process of producing alcohols which comprises treating with hydrogen an anhydride of an aliphatic carboxylic acid, said acid containing more than one carbon atom per carboxyl group at a temperature in excess of 200 C. and under a pressure in excess of 10 atmospheres in the presence of copper chromite. Y

3. A process in accordance with claim 2 characterized in that the reaction is carried out at a temperature between about 300 C. and about ing more than one carbon atom percarboxyl group at a temperature in excess of 200 C. and under a pressure in excess of 10 atmospheres, in the presence of a copper-containing hydrogenation catalyst activated by a substance comprising an oxide of chromium.

5. The process of producing alcohols which comprises treating with hydrogen an anhydride of an aliphatic carboxylic acid containing more than one carbon atom per carboxyl group at a temperature in excess of 200 C. and under a pressure in excess of 10 atmospheres, in the presence of zinc chromite promoted with copper chromite.

6. The process of producing alcohols which comprises treating acetic anhydride with hydrogen at a temperature in excess of 200 C. and under a pressure in excess of ten atmospheres in the presence of zinc chromite promoted with copper chromite.

WILBUR A. LAZIER.

CERTIFICATE OF CORRECTION.

Patent n 2,275,1 2; March 19m.

WILBUR A.- LAZIER.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, first column, 11 1 2, for "3oo lbs./sq. in." read ooo lbs./ sq. in.--; and,

that the said Letters Patent should be read with this correction therein that the seine mdy conform to the record of the case in the Patent Office.

Signed and sealed. this 5th day of May, A. D. 1912.

Henry Van Ar sdale, 1) Acting Commissioner of Patents. 

